Optical semiconductor devices such as LED (Light Emitting Diode) have merits such as reduced size, high efficiency, bright color, long life without burning out, high performance, and resistance to vibration and repeated ON/OFF switching, and therefore, these devices are widely used as various indicators and light sources. The material which has been widely used for producing the case of the optical semiconductor apparatus using such optical semiconductor device is polyphthalamide resin (PPA).
However, with the dramatic advance in the optical semiconductor technology, optical semiconductor apparatus has experienced rapid increase in the power and use of shorter wavelength. Encapsulation of the optical semiconductor device and the case produced by using the conventional PPA resin experiences severe deterioration in the prolonged use as well as color inconsistency, peeling, and loss of mechanical strength. There is a request for solving such problems in an efficient manner.
More specifically, Japanese Patent No. 2656336 discloses an optical semiconductor apparatus in which the resin used for the encapsulation is a B-stage epoxy resin for encapsulating an optical semiconductor comprising an epoxy resin, a curing agent, and a curing aid, and such components are homogeneously mixed at the molecular level. The epoxy resin used is mainly bisphenol A epoxy resin or bisphenol F epoxy resin, and use of triglycidllyl isocyanate and the like is also indicated. However, in the Examples, a small amount of triglycidyl isocyanate is used by adding to the bisphenol A or the bisphenol F epoxy resin. In the investigation by the inventors of the present invention, this B stage epoxy resin composition for encapsulating an optical semiconductor has been found to experience yellowing when left at high temperature for a long time.
Japanese Patent Application Laid-Open Nos. 2000-196151, 2003-224305, and 2005-306952 discloses use of a triazine derivative epoxy resin in an epoxy resin composition for encapsulating LED light-emitting device. However, the problem of yellowing after leaving at an elevated temperature or after using a prolonged period was not fully obviated by these resin compositions.
Japanese Patent Application Laid-Open No. 2006-77234 discloses a resin composition for encapsulating an LED device containing an organopolysiloxane having a weight average molecular weight of at least 5×103 and a condensation catalyst. However, this organopolysiloxane needs to be a transparent organopolysiloxane which is liquid at room temperature, and such organopolysiloxane is inadequate for use in transfer molding or compression molding.
In addition to the publications as mentioned above, the prior art publications which may be relevant with the present invention include the following documents:
Japanese Patent No. 3512732,
Japanese Patent Application Laid-Open No. 2001-234032,
Japanese Patent Application Laid-Open No. 2002-302533,
Japanese Patent Application Laid-Open No. 9-310007, and
Japanese Patent Application Laid-Open No. 2001-316591.
In addition, size of the molded package has recently become increasingly large as in the case of MAP (matrix array package), and this has resulted in the severer warpage after curing and invited various troubles in the course of package transportation and cutting into individual units.